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Evaluate the value of an arithmetic expression in Reverse Polish Notation.
Valid operators are +, -, *, /. Each operand may be an integer or another expression.
Some examples:
["2", "1", "+", "3", "*"] -> ((2 + 1) * 3) -> 9 ["4", "13", "5", "/", "+"] -> (4 + (13 / 5)) -> 6
class Solution{ private: bool isOperator(string s){ if(s.length()==1 && string("+-*/").find(s) != string::npos) return true; else return false; } public: int evalRPN(vector<string>& tokens){ stack<int> s; for (string token : tokens){ if(!isOperator(token)){ s.push(stoi(token)); }else{ int y = s.top(); s.pop(); int x = s.top(); s.pop(); if(token == "+"){ s.push(x+y); }else if(token == "-"){ s.push(x-y); }else if(token == "*"){ s.push(x*y); }else if(token == "/"){ s.push(x/y); } } } return s.top(); } };
Evaluate Reverse Polish Notation
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原文地址：http://www.cnblogs.com/wxquare/p/5928928.html
